Question

A weightless rod CD, 1.0m long is acted upon by horizontal forces of 2N, 4N, 8N is shown in the figure. What force will be necessary to produce equilibrium? 2N 2N. 8N
!............................!................20......... ..!
100. 60. !
4N

Answer 1

Assume that the forces are acting the following way:

(2N)-->....................(4N)-->.....................<--(8N).

To achieve equilibrium, the sum of all forces must be 0. Forces acting to the right are positive, negative forces acting to the left:

$$\sum F=2+4-8+x=0,$$ $$x=8-4-2=2 \text{ N}.$$